How exactly does the unified namespace (UNS) simplify system integration?
To answer this question let’s first examine the problem of adding two new systems to a typical data infrastructure of a plant.
Let’s imagine were developing an application that requires process data (gas temperature and pressure) of a vacuum furnace for each produced batch to calculate some result. The required input data is stored in a SCADA historian and MES respectively. So we connect the application directly to the historian and MES and calculate the desired process values per batch.
Now imagine we need a second application that not only requires data from the historian and MES, but also the result of the first application. Now, we would need to connect three systems to the second application: the historian, MES and the first application.
Integrating the two applications therefore requires five connections between systems. Any additional application would require even more connections. The UNS avoids this complexity via a publish-subscribe (pub/sub) architecture.
Compare the pub/sub architecture to a bicycle wheel: the UNS is the central hub to which individual spokes, i.e. the systems (historian, MES) are connected. Each of this systems subscribes to (receives data) and publishes (sends data) from/to the UNS. Note that the individual systems don’t need to know about the existence of other systems - they just need to be able to find their desired data in the UNS.
So what would our system integration challenge look like under the pub/sub architecture of the UNS?
- Connecting the first application would mean subscribing to the UNS to access the historian and MES data. The application would also publish the result to the UNS for use by any future system.
- Connecting the second application is analogous: subscribe to the UNS and consume the data from the historian, MES and the first application. Optionally, it could publish its result to the UNS.
This way, adding any new system is like adding one additional spoke to a bicycle wheel. The magic is that each individual system doesn’t need to know about the configuration of the other systems.